Disadvantages of exterior wood furnaces
We were thrilled when Mark's
mom gave us an external wood
a couple of years ago, and we are still very grateful. However,
over time, we've discovered that external wood furnaces have a variety
of problems associated with them:
- Extremely inefficient.
Even the most efficient new wood furnance I could find in my web
searches (the Mini-Caddy, listed as an Energy Star furnace, and
pictured here) is vastly
inferior to moderately efficient wood stoves. You can download
a list of EPA certified wood stoves
which will tell you the emissions and efficiency of all tested
models. The Caddy, which the Mini-Caddy is based on, has 6.6 g/hr
emissions and 63% efficiency. Compare it, for example, to the
Drolet Savannah wood stove (which has slightly less output than the
Mini-Caddy and is much
cheaper) --- 6.28 g/hr emissions and 75% efficiency.
- Expensive. We got
very lucky and were given our furnace as a gift, so
I wasn't prepared for the price tag when we considered upgrading to a
more efficient model. The Mini-Caddy seems to retail for
somewhere in the $2,000 range, compared to efficient, non-catalytic
wood stoves that can be got for closer to $700 (and which also have
efficiency, don't forget.) You can get a 30% federal tax credit
on either purchase.
- Not suited
for indoor use. After finishing up the East Wing, we moved
in our wood furnace, figuring that we'd be able to capture some of the
heat previously lost to the outside air. I know that the term "exterior
wood furnace" should have tipped me off, but we were shocked at how
smoky the East Wing got when we lit our first fire this year.
Granted, our model (LTD Limited by Jordahl Mfg.) is very old, and its
drawing problem may not be
found in more modern wood furnaces.
- Fails during power outages.
electricity to turn on the electric fan, we had to burn huge fires in
our furnace to keep the trailer at all habitable during last year's 10
day power outage.
- Is meant to
heat the whole house rather than a small section. You have
to burn a lot more wood in general to keep your house warm using an
exterior furnace since you depend on fans to move the hot air
throughout the house. With an indoor wood stove, you can situate
the stove in the population center of the house and burn small fires to
heat just that area.
All told, our exterior
wood furnace has definitely been better than
heating with electric space heaters, but we run through wood like
nobody's business. This week, I'm going to post about some of the
options we're considering --- I suspect you'll all have good advice, so
please chime in!
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Edited to add:
Learn how to safely install an energy-efficient wood stove in a moibile
home in Trailersteading. Now available for
$1.99 on Amazon.